The double bitted key is a type 2 NATO 10 Lever Mersey, but the bits are not detachable, it is a fixed bit built up from individual laminated sections.
That type followed on from the original type 1 which were moulded plastic over a thin steel core.
The laminated type you have there were superseded by solid cast brass keys finish machined and then later by bronze. The Later locks/ keys also had an extra 2 levers in each stack making them 14 lever, along with numerous other physical changes.
